The air conditioner (Penguin II from Dometic) failed in July 2015 when a tube split and I lost all refrigerant. Fortunately I got it fixed under extended warranty. The old Penguin II was a good bit louder than the new system. The old A/C had a horizontal compressor while the new one has a vertical compressor. In addition, Dometic had a free kit available to reduce the noise. You had to contact Dometic with the part number and serial number of your A/C. The sent you a kit with some new bushings and isolating tape/foam. I got it before the original A/C failed and it didn't seem to make much of a difference when I installed it.
One other possibility that I read about from another Camplite owner. He had a very noisy A/C and found that when it was mounted on the camper the mounting bolts were pushed hard against the mounting holes in the camper, rather than somewhat centered. This transmitted vibration from the A/C into the camper's frame which would resonate from the vibration, making it really loud. He loosened the mounting bolts and tried to reduce some of that pressure by shifting the A/C a bit. It made a big difference.
The non-ducted units will always be noisy, but if your seems to be really excessive and it seems like the whole camper is vibrating from the A/C; you may want to check the mounting.
